1 cup real butter – divided
1 1/4 cup Coca-Cola® – divided
1 oz. square semi-sweet baking chocolate
3/4 cup miniature marshmallows
2 1/3 cups all-purpose flour
1 1/4 cup unsweetened cocoa powder – divided
1 1/2 tsp. baking powder
1 tsp. baking soda
1/2 tsp. salt
2 cup granulated sugar
1/2 cup shortening
1/2 cup vegetable oil
3 tsp. vanilla extract – divided
3/4 cup buttermilk
1/4 cup chocolate syrup
3 cups powdered sugar
In a saucepan, bring 1/2 cup butter, 1 cup cola, and chocolate to a boil. Remove from heat and stir in marshmallows until dissolved. Set aside and allow to cool to room temperature.
In a bowl, Combine flour, 3/4 cup cocoa powder, baking powder, baking soda, and salt; set aside.
With an electric mixer, beat together sugar, shortening, oil, and 2 tsp. vanilla until fluffy; beat in eggs and buttermilk. Beat in 1/2 of the dry mixture, scraping the sides of the bowl often. Beat in cooled cola mixture. Add remaining dry mixture and beat for 4 minutes; batter will be thick.
Pour batter into a greased and floured 13″ X 9″ X 2″ baking pan. Bake on top rack of a 350 degree oven for 35-40 minutes, or until toothpick inserted in center comes out clean.
Cream butter with an electric mixer. Beat in 1/2 cup cocoa powder, 1/4 cup cola, chocolate syrup, and 1 tsp. vanilla. Slowly add powdered sugar, scraping the sides of the bowl often, while beating with the mixer. If frosting seems dry, add small amounts of cola until you reach desired consistency.
Frost cake while warm.